Standalone flex circuit for intravascular imaging device and associated devices, systems, and methods

ABSTRACT

An intravascular imaging device ( 102 ) is provided. In some embodiments, the intravascular imaging device includes a flexible elongate member sized and shaped for insertion into a vessel of a patient, the flexible elongate member having a proximal portion and a distal portion; and an imaging assembly ( 110 ) disposed at the distal portion of the flexible elongate member, the imaging assembly including a flex circuit ( 214 ) positioned directly around the flexible elongate member. In some embodiments, a method of assembling an intravascular imaging device includes obtaining a flex circuit including a first layer having a plurality of transducers and a second layer having an acoustic backing material; and positioning the flex circuit directly around a distal portion of a flexible elongate member.

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/EP2017/057562, filed on Mar.30, 2017, which claims the benefit of Provisional Application Serial No.62/315,416, filed Mar. 30, 2016. These applications are herebyincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to intravascular ultrasound(IVUS) imaging and, in particular, to the structure of an intravascularimaging device. For example, the structure can include a distal supportmember having a conductive portion that facilitates communication ofelectrical signals between a conductor and a flex circuit of theintravascular imaging device.

BACKGROUND

Intravascular ultrasound (IVUS) imaging is widely used in interventionalcardiology as a diagnostic tool for assessing a diseased vessel, such asan artery, within the human body to determine the need for treatment, toguide the intervention, and/or to assess its effectiveness. An IVUSdevice including one or more ultrasound transducers is passed into thevessel and guided to the area to be imaged. The transducers emitultrasonic energy in order to create an image of the vessel of interest.Ultrasonic waves are partially reflected by discontinuities arising fromtissue structures (such as the various layers of the vessel wall), redblood cells, and other features of interest. Echoes from the reflectedwaves are received by the transducer and passed along to an IVUS imagingsystem. The imaging system processes the received ultrasound echoes toproduce a cross-sectional image of the vessel where the device isplaced.

Solid-state (also known as synthetic-aperture) IVUS catheters are one ofthe two types of IVUS devices commonly used today, the other type beingthe rotational IVUS catheter. Solid-state IVUS catheters carry a scannerassembly that includes an array of ultrasound transducers distributedaround its circumference along with one or more integrated circuitcontroller chips mounted adjacent to the transducer array. Thecontrollers select individual transducer elements (or groups ofelements) for transmitting an ultrasound pulse and for receiving theultrasound echo signal. By stepping through a sequence oftransmit-receive pairs, the solid-state IVUS system can synthesize theeffect of a mechanically scanned ultrasound transducer but withoutmoving parts (hence the solid-state designation). Since there is norotating mechanical element, the transducer array can be placed indirect contact with the blood and vessel tissue with minimal risk ofvessel trauma. Furthermore, because there is no rotating element, theelectrical interface is simplified. The solid-state scanner can be wireddirectly to the imaging system with a simple electrical cable and astandard detachable electrical connector, rather than the complexrotating electrical interface required for a rotational IVUS device.

Manufacturing an intravascular imaging device that can efficientlytraverse physiology within the human body is challenging. In thatregard, components at the distal portion of the imaging device causes anarea of high rigidity in the intravascular device, which increase thelikelihood of kinking as the intravascular is steered throughvasculature.

Thus, there remains a need for intravascular ultrasound imaging systemthat overcomes the limitations of a rigid imaging assembly whileachieving efficient assembly and operation.

SUMMARY

Embodiments of the present disclosure provide an improved intravascularultrasound imaging system for generating images of a blood vessel. Adistal portion of an intravascular imaging device can include a flexcircuit. Whereas other imaging assemblies typically positioned the flexcircuit around a rigid support structure, imaging assemblies of thepresent disclosure wrap the flex circuit directly around a flexibleelongate member that extends along the length of the intravasculardevice. The flex circuit includes a plurality of transducers and a layerincluding acoustic backing material that facilitates operation of thetransducers. By omitting the rigid support structure, imaging assembliesof the present disclosure are advantageously more flexible.

In one embodiment, an intravascular imaging device is provided. Theintravascular imaging device includes a flexible elongate member sizedand shaped for insertion into a vessel of a patient, the flexibleelongate member having a proximal portion and a distal portion; and animaging assembly disposed at the distal portion of the flexible elongatemember, the imaging assembly including a flex circuit positioneddirectly around the flexible elongate member.

In some embodiments, the flex circuit comprises first layer having aplurality of transducers and a second layer having an acoustic backingmaterial. In some embodiments, the first layer is positioned over thesecond layer. In some embodiments, the acoustic backing materialcomprises at least one of cerium oxide, an epoxy, tungsten,polymethylpentene, or crosslinked polystyrene. In some embodiments, theflex circuit further comprises a third layer comprising a first flexiblesubstrate. In some embodiments, the third layer is positioned over thefirst layer. In some embodiments, the device further includes a fourthlayer comprising a second flexible substrate. In some embodiments, thesecond layer is positioned over the fourth layer. In some embodiments,the flex circuit further comprises a plurality of controllers incommunication with the plurality of transducers. In some embodiments,the flexible elongate member comprises an outer member and an innermember. In some embodiments, the flex circuit is positioned directlyaround the outer member.

In one embodiment, a method of assembling an intravascular imagingdevice is provided. The method includes obtaining a flex circuitincluding a first layer having a plurality of transducers and a secondlayer having an acoustic backing material; and positioning the flexcircuit directly around a distal portion of a flexible elongate member.

In some embodiments, the obtaining includes forming the flex circuitsuch that the first layer is positioned over the second layer. In someembodiments, the forming further includes depositing the acousticbacking material over a first flexible substrate. In some embodiments,the acoustic backing material comprises at least one of cerium oxide, anepoxy, tungsten, polymethylpentene, or crosslinked polystyrene. In someembodiments, the forming further includes positioning a second flexiblesubstrate over the first layer. In some embodiments, the flex circuitfurther includes a plurality of controllers in communication with theplurality of transducers. In some embodiments, the flexible elongatemember comprises an inner member and an outer member, and wherein flexcircuit is positioned directly around the outer member. In someembodiments, the method further includes coupling a distal member to atleast one of the flex circuit or the flexible elongate member.

Additional aspects, features, and advantages of the present disclosurewill become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present disclosure will be describedwith reference to the accompanying drawings, of which:

FIG. 1 is a diagrammatic schematic view of an imaging system, accordingto aspects of the present disclosure.

FIG. 2 is a diagrammatic top view of a scanner assembly in a flatconfiguration, according to aspects of the present disclosure.

FIG. 3 is a diagrammatic side view of a scanner assembly in a rolledconfiguration around a support member, according to aspects of thepresent disclosure.

FIG. 4 is a diagrammatic cross-sectional side view of a distal portionof an intravascular device, according to aspects of the presentdisclosure.

FIG. 5 is a diagrammatic cross-sectional side view of a distal portionof an intravascular device, according to aspects of the presentdisclosure.

FIG. 6 is a diagrammatic cross-sectional side view of a flex circuit,according to aspects of the present disclosure.

FIG. 7 is a flow diagram of a method of assembling an intravasculardevice, according to aspects of the present disclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It is nevertheless understood that no limitation tothe scope of the disclosure is intended. Any alterations and furthermodifications to the described devices, systems, and methods, and anyfurther application of the principles of the present disclosure arefully contemplated and included within the present disclosure as wouldnormally occur to one skilled in the art to which the disclosurerelates. For example, while the focusing system is described in terms ofcardiovascular imaging, it is understood that it is not intended to belimited to this application. The system is equally well suited to anyapplication requiring imaging within a confined cavity. In particular,it is fully contemplated that the features, components, and/or stepsdescribed with respect to one embodiment may be combined with thefeatures, components, and/or steps described with respect to otherembodiments of the present disclosure. For the sake of brevity, however,the numerous iterations of these combinations will not be describedseparately.

FIG. 1 is a diagrammatic schematic view of an intravascular ultrasound(IVUS) imaging system 100, according to aspects of the presentdisclosure. The IVUS imaging system 100 may include a solid-state IVUSdevice 102 such as a catheter, guide wire, or guide catheter, a patientinterface module (PIM) 104, an IVUS processing system or console 106,and a monitor 108.

At a high level, the IVUS device 102 emits ultrasonic energy from atransducer array 124 included in scanner assembly 110 mounted near adistal end of the catheter device. The ultrasonic energy is reflected bytissue structures in the medium, such as a vessel 120, surrounding thescanner assembly 110, and the ultrasound echo signals are received bythe transducer array 124. The PIM 104 transfers the received echosignals to the console or computer 106 where the ultrasound image(including the flow information) is reconstructed and displayed on themonitor 108. The console or computer 106 can include a processor and amemory. The computer or computing device 106 can be operable tofacilitate the features of the IVUS imaging system 100 described herein.For example, the processor can execute computer readable instructionsstored on the non-transitory tangible computer readable medium.

The PIM 104 facilitates communication of signals between the IVUSconsole 106 and the scanner assembly 110 included in the IVUS device102. This communication includes the steps of: (1) providing commands tointegrated circuit controller chip(s) 206A, 206B, illustrated in FIG. 2,included in the scanner assembly 110 to select the particular transducerarray element(s) to be used for transmit and receive, (2) providing thetransmit trigger signals to the integrated circuit controller chip(s)206A, 206B included in the scanner assembly 110 to activate thetransmitter circuitry to generate an electrical pulse to excite theselected transducer array element(s), and/or (3) accepting amplifiedecho signals received from the selected transducer array element(s) viaamplifiers included on the integrated circuit controller chip(s) 126 ofthe scanner assembly 110. In some embodiments, the PIM 104 performspreliminary processing of the echo data prior to relaying the data tothe console 106. In examples of such embodiments, the PIM 104 performsamplification, filtering, and/or aggregating of the data. In anembodiment, the PIM 104 also supplies high- and low-voltage DC power tosupport operation of the device 102 including circuitry within thescanner assembly 110.

The IVUS console 106 receives the echo data from the scanner assembly110 by way of the PIM 104 and processes the data to reconstruct an imageof the tissue structures in the medium surrounding the scanner assembly110. The console 106 outputs image data such that an image of the vessel120, such as a cross-sectional image of the vessel 120, is displayed onthe monitor 108. Vessel 120 may represent fluid filled or surroundedstructures, both natural and man-made. The vessel 120 may be within abody of a patient. The vessel 120 may be a blood vessel, as an artery ora vein of a patient's vascular system, including cardiac vasculature,peripheral vasculature, neural vasculature, renal vasculature, and/or orany other suitable lumen inside the body. For example, the device 102may be used to examine any number of anatomical locations and tissuetypes, including without limitation, organs including the liver, heart,kidneys, gall bladder, pancreas, lungs; ducts; intestines; nervoussystem structures including the brain, dural sac, spinal cord andperipheral nerves; the urinary tract; as well as valves within theblood, chambers or other parts of the heart, and/or other systems of thebody. In addition to natural structures, the device 102 may be may beused to examine man-made structures such as, but without limitation,heart valves, stents, shunts, filters and other devices.

In some embodiments, the IVUS device includes some features similar totraditional solid-state IVUS catheters, such as the EagleEye® catheteravailable from Volcano Corporation and those disclosed in U.S. Pat. No.7,846,101 hereby incorporated by reference in its entirety. For example,the IVUS device 102 includes the scanner assembly 110 near a distal endof the device 102 and a transmission line bundle 112 extending along thelongitudinal body of the device 102. The transmission line bundle orcable 112 can include a plurality of conductors, including one, two,three, four, five, six, seven, or more conductors 218 (FIG. 2). It isunderstood that any suitable gauge wire can be used for the conductors218. In an embodiment, the cable 112 can include a four-conductortransmission line arrangement with, e.g., 41 AWG gauge wires. In anembodiment, the cable 112 can include a seven-conductor transmissionline arrangement utilizing, e.g., 44 AWG gauge wires. In someembodiments, 43 AWG gauge wires can be used.

The transmission line bundle 112 terminates in a PIM connector 114 at aproximal end of the device 102. The PIM connector 114 electricallycouples the transmission line bundle 112 to the PIM 104 and physicallycouples the IVUS device 102 to the PIM 104. In an embodiment, the IVUSdevice 102 further includes a guide wire exit port 116. Accordingly, insome instances the IVUS device is a rapid-exchange catheter. The guidewire exit port 116 allows a guide wire 118 to be inserted towards thedistal end in order to direct the device 102 through the vessel 120.

FIG. 2 is a top view of a portion of an ultrasound scanner assembly 110according to an embodiment of the present disclosure. The assembly 110includes a transducer array 124 formed in a transducer region 204 andtransducer control logic dies 206 (including dies 206A and 206B) formedin a control region 208, with a transition region 210 disposedtherebetween. The transducer control logic dies 206 and the transducers212 are mounted on a flex circuit 214 that is shown in a flatconfiguration in FIG. 2. FIG. 3 illustrates a rolled configuration ofthe flex circuit 214. The transducer array 202 is a non-limiting exampleof a medical sensor element and/or a medical sensor element array. Thetransducer control logic dies 206 is a non-limiting example of a controlcircuit. The transducer region 204 is disposed adjacent a distal portion220 of the flex circuit 214. The control region 208 is disposed adjacentthe proximal portion 222 of the flex circuit 214. The transition region210 is disposed between the control region 208 and the transducer region204. Dimensions of the transducer region 204, the control region 208,and the transition region 210 (e.g., lengths 225, 227, 229) can vary indifferent embodiments. In some embodiments, the lengths 225, 227, 229can be substantially similar or a length 227 of the transition region210 can be greater than lengths 225, 229 of the transducer region andcontroller region, respectively. While the imaging assembly 110 isdescribed as including a flex circuit, it is understood that thetransducers and/or controllers may be arranged to form the imagingassembly 110 in other configurations, including those omitting a flexcircuit.

The transducer array 124 may include any number and type of ultrasoundtransducers 212, although for clarity only a limited number ofultrasound transducers are illustrated in FIG. 2. In an embodiment, thetransducer array 124 includes 64 individual ultrasound transducers 212.In a further embodiment, the transducer array 124 includes 32 ultrasoundtransducers 212. Other numbers are both contemplated and provided for.With respect to the types of transducers, in an embodiment, theultrasound transducers 124 are piezoelectric micromachined ultrasoundtransducers (PMUTs) fabricated on a microelectromechanical system (MEMS)substrate using a polymer piezoelectric material, for example asdisclosed in U.S. Pat. No. 6,641,540, which is hereby incorporated byreference in its entirety. In alternate embodiments, the transducerarray includes piezoelectric zirconate transducers (PZT) transducerssuch as bulk PZT transducers, capacitive micromachined ultrasoundtransducers (cMUTs), single crystal piezoelectric materials, othersuitable ultrasound transmitters and receivers, and/or combinationsthereof.

The scanner assembly 110 may include various transducer control logic,which in the illustrated embodiment is divided into discrete controllogic dies 206. In various examples, the control logic of the scannerassembly 110 performs: decoding control signals sent by the PIM 104across the cable 112, driving one or more transducers 212 to emit anultrasonic signal, selecting one or more transducers 212 to receive areflected echo of the ultrasonic signal, amplifying a signalrepresenting the received echo, and/or transmitting the signal to thePIM across the cable 112. In the illustrated embodiment, a scannerassembly 110 having 64 ultrasound transducers 212 divides the controllogic across nine control logic dies 206, of which five are shown inFIG. 2. Designs incorporating other numbers of control logic dies 206including 8, 9, 16, 17 and more are utilized in other embodiments. Ingeneral, the control logic dies 206 are characterized by the number oftransducers they are capable of driving, and exemplary control logicdies 206 drive 4, 8, and/or 16 transducers.

The control logic dies are not necessarily homogenous. In someembodiments, a single controller is designated a master control logicdie 206A and contains the communication interface for the cable 112.Accordingly, the master control circuit may include control logic thatdecodes control signals received over the cable 112, transmits controlresponses over the cable 112, amplifies echo signals, and/or transmitsthe echo signals over the cable 112. The remaining controllers are slavecontrollers 206B. The slave controllers 206B may include control logicthat drives a transducer 212 to emit an ultrasonic signal and selects atransducer 212 to receive an echo. In the depicted embodiment, themaster controller 206A does not directly control any transducers 212. Inother embodiments, the master controller 206A drives the same number oftransducers 212 as the slave controllers 206B or drives a reduced set oftransducers 212 as compared to the slave controllers 206B. In anexemplary embodiment, a single master controller 206A and eight slavecontrollers 206B are provided with eight transducers assigned to eachslave controller 206B.

The flex circuit 214, on which the transducer control logic dies 206 andthe transducers 212 are mounted, provides structural support andinterconnects for electrical coupling. The flex circuit 214 may beconstructed to include a film layer of a flexible polyimide materialsuch as KAPTON™ (trademark of DuPont). Other suitable materials includepolyester films, polyimide films, polyethylene napthalate films, orpolyetherimide films, other flexible printed semiconductor substrates aswell as products such as Upilex® (registered trademark of UbeIndustries) and TEFLON® (registered trademark of E.I. du Pont). In theflat configuration illustrated in FIG. 2, the flex circuit 214 has agenerally rectangular shape. As shown and described herein, the flexcircuit 214 is configured to be wrapped around a support member 230(FIG. 3) to form a cylindrical toroid in some instances. Therefore, thethickness of the film layer of the flex circuit 214 is generally relatedto the degree of curvature in the final assembled scanner assembly 110.In some embodiments, the film layer is between 5 μm and 100 μm, withsome particular embodiments being between 12.7 μm and 25.1 μm.

To electrically interconnect the control logic dies 206 and thetransducers 212, in an embodiment, the flex circuit 214 further includesconductive traces 216 formed on the film layer that carry signalsbetween the control logic dies 206 and the transducers 212. Inparticular, the conductive traces 216 providing communication betweenthe control logic dies 206 and the transducers 212 extend along the flexcircuit 214 within the transition region 210. In some instances, theconductive traces 216 can also facilitate electrical communicationbetween the master controller 206A and the slave controllers 206B. Theconductive traces 216 can also provide a set of conductive pads thatcontact the conductors 218 of cable 112 when the conductors 218 of thecable 112 are mechanically and electrically coupled to the flex circuit214. Suitable materials for the conductive traces 216 include copper,gold, aluminum, silver, tantalum, nickel, and tin, and may be depositedon the flex circuit 214 by processes such as sputtering, plating, andetching. In an embodiment, the flex circuit 214 includes a chromiumadhesion layer. The width and thickness of the conductive traces 216 areselected to provide proper conductivity and resilience when the flexcircuit 214 is rolled. In that regard, an exemplary range for thethickness of a conductive trace 216 and/or conductive pad is between10-50 μm. For example, in an embodiment, 20 μm conductive traces 216 areseparated by 20 μm of space. The width of a conductive trace 216 on theflex circuit 214 may be further determined by the width of the conductor218 to be coupled to the trace/pad.

The flex circuit 214 can include a conductor interface 220 in someembodiments. The conductor interface 220 can be a location of the flexcircuit 214 where the conductors 218 of the cable 114 are coupled to theflex circuit 214. For example, the bare conductors of the cable 114 areelectrically coupled to the flex circuit 214 at the conductor interface220. The conductor interface 220 can be tab extending from the main bodyof flex circuit 214. In that regard, the main body of the flex circuit214 can refer collectively to the transducer region 204, controllerregion 208, and the transition region 210. In the illustratedembodiment, the conductor interface 220 extends from the proximalportion 222 of the flex circuit 214. In other embodiments, the conductorinterface 220 is positioned at other parts of the flex circuit 214, suchas the distal portion 220, or the flex circuit 214 omits the conductorinterface 220. A value of a dimension of the tab or conductor interface220, such as a width 224, can be less than the value of a dimension ofthe main body of the flex circuit 214, such as a width 226. In someembodiments, the substrate forming the conductor interface 220 is madeof the same material(s) and/or is similarly flexible as the flex circuit214. In other embodiments, the conductor interface 220 is made ofdifferent materials and/or is comparatively more rigid than the flexcircuit 214. For example, the conductor interface 220 can be made of aplastic, thermoplastic, polymer, hard polymer, etc., includingpolyoxymethylene (e.g., DELRIN®), polyether ether ketone (PEEK), nylon,and/or other suitable materials. As described in greater detail herein,the support member 230, the flex circuit 214, the conductor interface220 and/or the conductor(s) 218 can be variously configured tofacilitate efficient manufacturing and operation of the scanner assembly110.

In some instances, the scanner assembly 110 is transitioned from a flatconfiguration (FIG. 2) to a rolled or more cylindrical configuration(FIGS. 3 and 4). For example, in some embodiments, techniques areutilized as disclosed in one or more of U.S. Pat. No. 6,776,763, titled“ULTRASONIC TRANSDUCER ARRAY AND METHOD OF MANUFACTURING THE SAME” andU.S. Pat. No. 7,226,417, titled “HIGH RESOLUTION INTRAVASCULARULTRASOUND TRANSDUCER ASSEMBLY HAVING A FLEXIBLE SUBSTRATE,” each ofwhich is hereby incorporated by reference in its entirety.

As shown in FIGS. 3 and 4, the flex circuit 214 is positioned around thesupport member 230 in the rolled configuration. FIG. 3 is a diagrammaticside view with the flex circuit 214 in the rolled configuration aroundthe support member 230, according to aspects of the present disclosure.FIG. 4 is a diagrammatic cross-sectional side view of a distal portionof the intravascular device 110, including the flex circuit 214 and thesupport member 230, according to aspects of the present disclosure.

The support member 230 can be referenced as a unibody in some instances.The support member 230 can be composed of a metallic material, such asstainless steel, or non-metallic material, such as a plastic or polymeras described in U.S. Provisional Application No. 61/985,220, “Pre-DopedSolid Substrate for Intravascular Devices,” filed Apr. 28, 2014, theentirety of which is hereby incorporated by reference herein. Thesupport member 230 can be ferrule having a distal portion 262 and aproximal portion 264. The support member 230 can define a lumen 236extending longitudinally therethrough. The lumen 236 is in communicationwith the exit port 116 and is sized and shaped to receive the guide wire118 (FIG. 1). The support member 230 can be manufactured accordingly toany suitable process. For example, the support member 230 can bemachined, such as by removing material from a blank to shape the supportmember 230, or molded, such as by an injection molding process. In someembodiments, the support member 230 may be integrally formed as aunitary structure, while in other embodiments the support member 230 maybe formed of different components, such as a ferrule and stands 242,244, that are fixedly coupled to one another.

Stands 242, 244 that extend vertically are provided at the distal andproximal portions 262, 264, respectively, of the support member 230. Thestands 242, 244 elevate and support the distal and proximal portions ofthe flex circuit 214. In that regard, portions of the flex circuit 214,such as the transducer portion 204, can be spaced from a central bodyportion of the support member 230 extending between the stands 242, 244.The stands 242, 244 can have the same outer diameter or different outerdiameters. For example, the distal stand 242 can have a larger orsmaller outer diameter than the proximal stand 244. To improve acousticperformance, any cavities between the flex circuit 214 and the surfaceof the support member 230 are filled with a backing material 246. Theliquid backing material 246 can be introduced between the flex circuit214 and the support member 230 via passageways 235 in the stands 242,244. In some embodiments, suction can be applied via the passageways 235of one of the stands 242, 244, while the liquid backing material 246 isfed between the flex circuit 214 and the support member 230 via thepassageways 235 of the other of the stands 242, 244. The backingmaterial can be cured to allow it to solidify and set. In variousembodiments, the support member 230 includes more than two stands 242,244, only one of the stands 242, 244, or neither of the stands. In thatregard the support member 230 can have an increased diameter distalportion 262 and/or increased diameter proximal portion 264 that is sizedand shaped to elevate and support the distal and/or proximal portions ofthe flex circuit 214.

The support member 230 can be substantially cylindrical in someembodiments. Other shapes of the support member 230 are alsocontemplated including geometrical, non-geometrical, symmetrical,non-symmetrical, cross-sectional profiles. Different portions thesupport member 230 can be variously shaped in other embodiments. Forexample, the proximal portion 264 can have a larger outer diameter thanthe outer diameters of the distal portion 262 or a central portionextending between the distal and proximal portions 262, 264. In someembodiments, an inner diameter of the support member 230 (e.g., thediameter of the lumen 236) can correspondingly increase or decrease asthe outer diameter changes. In other embodiments, the inner diameter ofthe support member 230 remains the same despite variations in the outerdiameter.

A proximal inner member 256 and a proximal outer member 254 are coupledto the proximal portion 264 of the support member 230. The proximalinner member 256 and/or the proximal outer member 254 can be flexibleelongate member that extend from proximal portion of the intravascular102, such as the proximal connector 114, to the imaging assembly 110.For example, the proximal inner member 256 can be received within aproximal flange 234. The proximal outer member 254 abuts and is incontact with the flex circuit 214. A distal member 252 is coupled to thedistal portion 262 of the support member 230. The distal member 252 canbe a flexible component that defines a distal most portion of theintravascular device 102. For example, the distal member 252 ispositioned around the distal flange 232. The distal member 252 can abutand be in contact with the flex circuit 214 and the stand 242. Thedistal member 252 can be the distal-most component of the intravasculardevice 102.

One or more adhesives can be disposed between various components at thedistal portion of the intravascular device 102. For example, one or moreof the flex circuit 214, the support member 230, the distal member 252,the proximal inner member 256, and/or the proximal outer member 254 canbe coupled to one another via an adhesive.

FIG. 5 is diagrammatic cross-sectional side view an embodiment of anintravascular device 300, including an imaging assembly 302. Theintravascular device 300 and the imaging assembly 302 may be similar tothe intravascular device 102 and the imaging assembly 110, in someaspects.

A flex circuit 314 of the imaging assembly 302 is positioned directlyaround the proximal member 254. For example, the flex circuit 314 may berolled into a cylindrical or cylindrical toroid configuration around theproximal member 254. The imaging assembly 302 does not include auni-body or support structure. By omitting the rigid support structurefrom the imaging assembly 302, distal portion of the intravasculardevice 300 is advantageously more flexible. For example, the componentsat the distal portion of the intravascular device 300, including theflex circuit 314, the proximal members 254, 256, and the distal member252, are formed of flexible materials. Accordingly, the intravasculardevice 3000 may more easily traverse tortuous physiology within apatient's body.

In the embodiments of FIG. 5, the flex circuit 314 is positioneddirectly around the outer member 254. In some embodiments, theintravascular device 300 includes only one proximal member. In suchembodiments, the flex circuit 314 can be positioned directly around theone proximal member.

FIG. 6 is a diagrammatic cross-sectional side of an embodiment of a flexcircuit 414. The flex circuit 414 can be wrapped directly around theproximal member 254. FIG. 6 illustrates layers of the flex circuit 414.In that regard, the flex circuit 414 includes a layer 415 in which theplurality of transducers 212 are positioned. For example, thetransducers 212 can be formed within the layer 415 according to anysuitable manufacturing technique(s), such as those described in U.S.Provisional App. No. 61/746,804, titled “Intravascular UltrasoundImaging Apparatus, Interface, Architecture, and Method ofManufacturing,” and filed Dec. 28, 2012, the entirety of which is herebyincorporated by reference herein. In some embodiments, the layer 415 isbetween approximately 50 μm and approximately 200 μm.

The layer 415 is positioned over a layer 410 including an acousticbacking material. The backing material facilitates operation of thetransducers 212 by improving acoustic performance. The acoustic backingmaterial can include one or more of cerium oxide, an epoxy such asEPO-TEK, a mix containing filler/additive materials such as tungsten,polymethylpentene, crosslinked polystyrene, and/other suitable materialsetc. The backing material may contain one or more fillers such astungsten, polymethylpentene, crosslinked polystyrene. In someembodiments, the layer 415 of transducers can be positioned overmultiple backing layers which together satisfy the acoustic requirementsof the transducers. The acoustic backing material may be formed on thelayer 410 using any suitable technique, including physical vapordeposition, chemical vapor deposition, chemical adsorption, physicaladsorption, dip coating, solvent evaporation, etc. In some embodiments,the layer 410 is between approximately 50 μm and approximately 200 μm.

The layer 410 can be positioned on the flexible substrate 405. A flexsubstrate layer 420 can also be positioned over the layer 415. Theflexible substrates 405, 420 provide structural integrity andflexibility to the flex circuit 414. The flexible substrates 405, 220can be a film layer of a flexible polyimide material such as KAPTON™(trademark of DuPont). Other suitable materials include polyester films,polyimide films, polyethylene napthalate films, or polyetherimide films,other flexible printed semiconductor substrates as well as products suchas Upilex® (registered trademark of Ube Industries) and TEFLON®(registered trademark of E.I. du Pont). In some embodiments, each of thelayers 405, 420 is between approximately 1 μm and approximately 100 μm.The layer 405 may be in contact with the proximal member 254 when theflex circuit 414 is wrapped around the proximal member 254.

The flex circuit 414 can also include a layer 425 including a pluralityof controllers (e.g., the controllers 206A, 206B). For example, thecontrollers can be formed within the layer 425 according to any suitabletechnique, such as those described in U.S. Provisional App. No.61/746,804, titled “Intravascular Ultrasound Imaging Apparatus,Interface, Architecture, and Method of Manufacturing,” and filed Dec.28, 2012, the entirety of which is hereby incorporated by referenceherein. The plurality of controllers of layer 425 is in electricalcommunication with the plurality of transducers 212 of layer 415. Inthat regard, conductive traces and/or electrical interconnects can beformed within the layers 415, 425. In some embodiments, the flex circuit414 includes an additional layer including electrical interconnectsestablishing electrically communication between controllers andtransducers.

In some embodiments, the flex circuit 414 can have a transducer segmentand controller segment. For example, the transducer segment can includethe layers 405, 410, 415, and 420. The controller segment can includethe layers 405, 425, and 420. The transducer segment and the controllersegment can be spaced from one another. For example, a flexiblesubstrate layer can extend longitudinally between the two segments. Thisflexible substrate layer can include conductive traces establishingelectrical communication between the controllers and the transducers. Insome embodiments, one of the transducer segment and the controllersegment may be implemented without a support member or uni-bodystructure in the intravascular device 102, while the other of thetransducer segment and the controller is implemented with a supportmember or uni-body structure. For example, the transducer segment may bewrapped around a support member including stands that elevate thetransducer segment from a main body of the support member. The spacebetween the transducer segment and the support member may be filled withan acoustic backing material. The controller segment may be implementedwithout a support member such that the controller segment is wrappeddirectly around the outer proximal member. Some exemplary arrangementsare described in U.S. Provisional App. No 62/315,406, filed on an Mar.30, 2016, the entirety of which is hereby incorporated by referenceherein.

FIG. 7 is a flow diagram of a method 400 of assembling an intravascularimaging device, including an imaging assembly with a support memberdescribed herein. It is understood that the steps of method 400 may beperformed in a different order than shown in FIG. 7, additional stepscan be provided before, during, and after the steps, and/or some of thesteps described can be replaced or eliminated in other embodiments. Thesteps of the method 400 can be carried out by a manufacturer of theintravascular imaging device.

At step 410, the method 400 includes forming a flex circuit. The flexcircuit includes electronic components, such as a plurality oftransducers and a plural of controllers, of an imaging assembly. Formingthe flex circuit can include, at step 420, depositing an acousticbacking material over a first flexible substrate. At step 430, formingthe flex circuit can include forming a layer having the plurality oftransducers over the acoustic backing material. At step 440, forming theflex circuit can include position a second flexible substrate over thelayer having the plurality of transducers. In some embodiments, formingthe flex circuit can additionally include forming a plurality ofcontrollers in a layer of the flex circuit. In some embodiments, theplurality of controllers can be formed in the same layer as theplurality of transducers. Forming the flex circuit can also includedisposing conductive traces facilitating electrical communicationbetween the transducers and controllers onto one or more layers of theflex circuit. In some embodiments, forming the flex circuit can includeforming an interconnect layer to establish electrical communicationbetween the transducers and controllers.

At step 450, the method 440 includes positioning the flex circuitdirectly around a distal portion of a flexible elongate member. In thatregard, the flex circuit may be formed (step 410-440) with the flexcircuit in a planar configuration. Step 450 can include transitioningthe flex circuit into a cylindrical or cylindrical toroid configuration,such as by wrapping, around the flexible elongate member. For example,the flexible elongate member can be an outer proximal member.

At step 460, the method 400 includes include coupling the flex circuitand/or flexible elongate member to a distal member that defines adistal-most end of the intravascular imaging device. The method 400 caninclude introducing adhesive to affix the flex circuit, the flexibleelongate member, the distal member, and/or other components of theintravascular imaging device.

The method 400 can additionally include electrically coupling aconductor the flex circuit. The intravascular device can include aplurality of conductors. The method 400 can also include positioning theone or more conductors within a flexible elongate member. Theconductor(s) can extend along a length of the intravascular device. Theconductor(s) can be threaded through the flex elongate member such that,e.g., the conductor(s) are positioned with a lumen of an outer memberand/or disposed between an inner member and an outer member.

Various embodiments of an intravascular device and/or imaging assemblycan include features described in U.S. Provisional App. No. 62/315,395,filed on Mar. 30, 2016, U.S. Provisional App. No. 62/315,406, filed onMar. 30, 2016, U.S. Provisional App. No. 62/315,421, filed on Mar. 30,2016, and U.S. Provisional App. No. 62/315,428, filed on Mar. 30, 2016,the entireties of which are hereby incorporated by reference herein.

Persons skilled in the art will recognize that the apparatus, systems,and methods described above can be modified in various ways.Accordingly, persons of ordinary skill in the art will appreciate thatthe embodiments encompassed by the present disclosure are not limited tothe particular exemplary embodiments described above. In that regard,although illustrative embodiments have been shown and described, a widerange of modification, change, and substitution is contemplated in theforegoing disclosure. It is understood that such variations may be madeto the foregoing without departing from the scope of the presentdisclosure. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the presentdisclosure.

What is claimed is:
 1. An intravascular imaging device comprising: aflexible elongate member sized and shaped for insertion into a vessel ofa patient, the flexible elongate member comprising: a proximal portionand a distal portion along a longitudinal direction; an outer surfaceand an inner surface along a radial direction; an imaging assemblydisposed at the distal portion of the flexible elongate member, whereinthe imaging assembly comprises a flex circuit, wherein the flex circuitcomprises: a length along the longitudinal direction; an outer surfaceand an inner surface along the radial direction; a plurality oftransducers; and a plurality of controllers in communication with theplurality of transducers, wherein the flex circuit encircles the outersurface of the flexible elongate member at the distal portion of theflexible elongate member such that: the inner surface of the flexcircuit forms a lumen of the intravascular imaging device; the distalportion of the flexible elongate member is disposed inside of the lumenand the proximal portion of the flexible elongate member is not disposedinside of the lumen; the outer surface of the flexible elongate memberat the distal portion of the flexible elongate member faces the innersurface of the flex circuit; the entire length of the flex circuit isoutside of the flexible elongate member in the radial direction at thedistal portion of the flexible elongate member; the plurality oftransducers and the plurality of controllers are outside of the flexibleelongate member in the radial direction at the distal portion of theflexible elongate member; the flex circuit is an outermost component ofthe intravascular imaging device in the radial direction at the distalportion of the flexible elongate member; and the flexible elongatemember is the outermost component of the intravascular imaging deviceproximal of the flex circuit.
 2. The device of claim 1, wherein the flexcircuit comprises a first layer having a plurality of transducers and asecond layer having an acoustic backing material.
 3. The device of claim2, wherein the first layer is positioned over the second layer.
 4. Thedevice of claim 2, wherein the acoustic backing material comprises atleast one of cerium oxide, an epoxy, tungsten, polymethylpentene, orcrosslinked polystyrene.
 5. The device of claim 4, wherein the flexcircuit further comprises a third layer comprising a first flexiblesubstrate.
 6. The device of claim 5, wherein the third layer ispositioned over the first layer.
 7. The device of claim 6, furthercomprising a fourth layer comprising a second flexible substrate.
 8. Thedevice of claim 7, wherein the second layer is positioned over thefourth layer.
 9. The device of claim 1, further comprising an innerflexible elongate member extending within a space defined by a profileof the flexible elongate member.
 10. The device of claim 1, wherein theproximal portion is in communication with a connector of theintravascular imaging device.
 11. The device of claim 1, wherein theflex circuit comprises a plurality of layers positioned on top of oneanother, wherein the flex circuit is positioned directly around theouter surface of the flexible elongate member such that innermost layerof the plurality of layers directly contacts the outer surface of theflexible elongate member.
 12. The device of claim 2, wherein the firstlayer and second layer of the flex circuit are spaced from the outersurface of the flex circuit and the inner surface of the flex circuit.13. The device of claim 12, wherein the flex circuit further comprises afirst flexible substrate defining the outer surface and a secondflexible substrate defining the inner surface.
 14. A method ofassembling an intravascular imaging device, the method comprising:obtaining a flex circuit including a first layer having a plurality oftransducers and a second layer having an acoustic backing material, theflex circuit comprising: a length along a longitudinal direction; and anouter surface and an inner surface along a radial direction; couplingthe inner surface of the flex circuit to an outer surface of a flexibleelongate member, the flexible elongate member comprising: a proximalportion and a distal portion along the longitudinal direction; and anouter surface and an inner surface along the radial direction; whereinthe flex circuit is disposed at the distal portion of the flexibleelongate member, and encircles the outer surface of the flexibleelongate member such that: the inner surface of the flex circuit forms alumen of the intravascular imaging device: the distal portion of theflexible elongate member is disposed inside of the lumen and theproximal portion of the flexible elongate member is not disposed insideof the lumen: the outer surface of the flexible elongate member at thedistal portion of the flexible elongate member faces the inner surfaceof the flex circuit the entire length of the flex circuit is outside ofthe flexible elongate member in the radial direction at the distalportion of the flexible elongate member; the plurality of transducersand the plurality of controllers are outside of the flexible elongatemember in the radial direction at the distal portion of the flexibleelongate member; the flex circuit is an outermost component of theintravascular imaging device in the radio direction at the distalportion of the flexible elongate member; and the flexible elongatemember is the outermost component of the intravascular imaging deviceproximal of the flex circuit.
 15. The method of claim 14, wherein theobtaining includes forming the flex circuit such that the first layer ispositioned over the second layer.
 16. The method of claim 15, whereinthe forming further includes: depositing the acoustic backing materialover a first flexible substrate.
 17. The method of claim 16, wherein theacoustic backing material comprises at least one of cerium oxide, anepoxy, tungsten, polymethylpentene, or crosslinked polystyrene.
 18. Themethod of claim 16, wherein the forming further includes: positioning asecond flexible substrate over the first layer.
 19. The method of claim14, wherein the flex circuit further includes a plurality of controllersin communication with the plurality of transducers.
 20. The method ofclaim 14, further comprising obtaining an inner flexible elongate memberextending within a space defined by a profile of the flexible elongatemember.
 21. The method of claim 20, further comprising: coupling adistal member to at least one of the flex circuit or the flexibleelongate member.
 22. The method of claim 14, wherein the proximalportion is in communication with a connector of the intravascularimaging device.